Projector

ABSTRACT

A projector includes a lamp that emits projection light to project 3D picture, in which a right eye image and a left eye image are represented in a time division manner, to an object, a synchronization signal transmission section which transmits shutter synchronization signal to glasses having a right eye shutter and a left eye shutter to control the opened state or the closed state of the right eye shutter and the left eye shutter, based on the signal indicating a displaying period of the right eye image and the left eye image of 3D picture, and a lamp drive section that supplies AC current having peak overlapping with a period when the right eye shutter of the glasses is in the opened state and peak overlapping with a period when the left eye shutter of the glasses is in the opened state to the lamp, based on the signal.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/046,388, filed Feb. 17, 2016, which is a continuation of U.S.application Ser. No. 14/598,120, filed Jan. 15, 2015, which is acontinuation of U.S. patent application Ser. No. 13/619,869, filed Sep.14, 2012, which claims priority to Japanese Patent Application No.2011-211115, filed Sep. 27, 2011. The foregoing applications areincorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a projector displayingthree-dimensional picture (a picture visible in stereoscopic view,referred to as 3D picture) and a technique improving the brightness ofimage perceived by a user through glasses for viewing 3D picture by auser.

2. Related Art

A display system displayable 3D picture has been known. In a case ofdisplaying 3D picture using such a displaying system, a right eyepicture and a left eye picture are sequentially displayed and arecomposited and displayed on the picture display device, and a user whoappreciates 3D picture wears glasses (referred to as 3D glasses) forviewing 3D picture separating the right eye picture and the left eyepicture. In JP-A-2009-25436, it is disclosed that a description that aright eye image and a left eye image are alternately displayed on thedisplay screen and shutter glasses having a right eye liquid crystalshutter and a left eye liquid crystal shutter are used as 3D glasses.When the right eye image is displayed, the right eye liquid crystalshutter is opened and the left eye liquid crystal shutter is closed.When the left eye image is displayed, the right eye liquid crystalshutter is closed and the left eye liquid crystal shutter is opened.

In JP-T-10-501919 and JP-T-2002-533884, a description that a highpressure electric discharge lamp turn-on circuit which applies an AClamp current to a high-pressure electric discharge lamp used as lightsource of the projector and turns-on the high-pressure electricdischarge lamp has been disclosed. The high pressure electric dischargelamp turn-on circuit described in the JP-T-10-501919 andJP-T-2002-533884 includes a control unit overlapping an additionalcurrent pulse having a similar polarity to a polarity of the half waveat a termination time of half wave of each polarity of AC lamp currentin order to reduce a flicker appearing in a projection image. Further,in the high pressure electric discharge lamp turn-on circuit indisclosed in JP-T-2002-533884, it is described that the control unitsynchronizes with image writing signal.

However, in JP-T-10-501919 and JP-T-2002-533884, there is no mention ofthe point such that when 3D picture is displayed by a projector,improving of the brightness of image viewed through 3D glasses by a userand suppressing of the increase in lamp drive power used as a projectionlight source in the projector are compatible.

SUMMARY

An advantage of some aspects of the invention is to allow that improvingof the brightness of image viewed through 3D glasses by a user andsuppressing of the increase of lamp drive power used as a projectionlight source in the projector are compatible when a 3D picture isdisplayed by the projector.

According to an aspect of the invention, there is provided a projectorincluding a lamp that emits projection light to project 3D picture, inwhich a right eye image and a left eye image are presented in a timedivision manner, to an object, a synchronization signal transmissionsection which transmits a shutter synchronization signal to a pair ofglasses having a right eye shutter and a left eye shutter which are inan opened state or a closed state independently, to control the openedstate or the closed state of the right eye shutter and the left eyeshutter, based on a signal indicating a displaying period of the righteye image and the left eye image of the 3D picture, and a lamp drivesection that supplies AC current having a peak overlapping with a periodwhen the right eye shutter is in the opened state and a peak overlappingwith a period when the left eye shutter is in the opened state to thelamp, based on the signal indicating the displaying period of the righteye image and the left eye image of the 3D picture.

According to such a projector, when displaying the 3D picture, improvingof the brightness of the image viewed through 3D glasses by a user andsuppressing of the increase of lamp drive power used as a projectionlight source in the projector are compatible.

It is preferable that, a phase with respect to the signal indicating adisplaying period of the right eye image and the left eye image of the3D picture of the peak of the AC current supplied by the lamp drive maybe set so that a value obtained by a integrating for a product of a lampbrightness and the transmissivity of the right eye shutter or the lefteye shutter in a predetermined period becomes maximum value.

In such a projector, the brightness of the image viewed through the 3Dglasses by a user can be improved compared to a case where a phase withrespect to the 3D picture signal of the peak of AC current supplied bythe lamp drive section is not set so that the value obtained by aintegrating for a product of the lamp brightness and the transmissivityof the right eye shutter or the left eye shutter in a predeterminedperiod become maximum value.

It is preferable that, the lamp drive section decreases the lampbrightness in a period in which both of the right eye shutter and theleft eye shutter of the glasses are in the closed state compared to aperiod in which either of the right eye shutter and the left eye shutteris in the opened state.

According to such a projector, a crosstalk can be decreased compared toa case where the lamp brightness is not decreased, compared to a periodin which either of the right eye shutter and the left eye shutter is inthe opened state, in a period in which both of the right eye shutter andthe left eye shutter of the glasses are in the closed state.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic diagram illustrating the overall configuration ofa display system according to an embodiment.

FIG. 2 is a plan view illustrating a configuration of a pictureprojection section of a projector.

FIG. 3 is a diagram illustrating an example of an external appearance ofglasses.

FIG. 4 is a block diagram illustrating a functional configuration of thedisplaying system.

FIG. 5 is a block diagram illustrating a configuration of a lamp drivesection.

FIG. 6 is a graph illustrating an example of writing start signal, lampdrive current and lamp brightness.

FIG. 7 is a diagram illustrating the creation timing of lamp brightnesspulses with respect to an operation of each section of the displaysystem in the embodiment.

FIG. 8 is a diagram illustrating creation timing of lamp brightnesspulses with respect to an operation of each section of the displaysystem in a comparative example.

FIG. 9 is a diagram illustrating the transmissivity of the glasses andthe lamp brightness in a comparative example.

FIG. 10 is a diagram illustrating an optical intensity measured over theglasses in an example shown in FIG. 9.

FIG. 11 is a diagram illustrating the transmissivity of the glasses andthe lamp brightness in the embodiment.

FIG. 12 is a diagram illustrating the optical intensity measured overthe glasses of an example in shown in FIG. 11.

FIG. 13 is a diagram illustrating the transmissivity of the glasses andthe lamp brightness in Modification Example 1.

FIG. 14 is a diagram illustrating the optical intensity measured overthe glasses in the example shown FIG. 13.

FIG. 15 is a diagram illustrating the transmissivity of the glasses andthe lamp brightness in Modification Example 2.

FIG. 16 is a diagram illustrating the optical intensity measured overthe glasses in the example shown FIG. 15.

DESCRIPTION OF EXEMPLARY EMBODIMENTS 1. Embodiment

FIG. 1 shows a diagram illustrating the overall configuration of adisplay system 1 according to an embodiment. The display system 1 has aprojector 10, glasses 20 and a screen SC. In example of FIG. 1, theprojector 10 is a front projector that projects an image according to aninputted picture signal from in front of the screen SC to the screen SC.Further, the projector 10 may be a rear projector that projects an imagefrom a rear side of the screen SC to the screen SC. In the embodiment, apicture indicating the picture signal inputted to the projector 10refers to a 3D picture by which a right eye image (hereinafter, referredto as “right eye image”) and an left eye image (hereinafter, referred toas “left eye image”) are alternately represented using a time-division(that is, slip off in terms of time). Individual still image whichconstitutes 3D picture is referred to a frame. Accordingly, in a case of3D picture, commonly, a right eye image and a left eye image are oneframe repeated at intervals. Further, the picture referred to herein isstands for a motion picture mainly, but may be a still image. The screenSC is an example of an object providing a surface displaying a pictureprojected from the projector 10. Instead of the screen SC, a wallsurface or the like may be used. The glasses 20 are 3D glasses forindependently viewing a right eye image and a left eye image in theright eye and the left eye of the user wearing the glasses 20.

FIG. 2 shows a plan view illustrating a configuration of a pictureprojection section (reference number 14 in FIG. 4) of the projector 10.In the example, the projector 10 is a three panel projector that aliquid crystal panels is used as a light valve for each color of RGB.

As shown in FIG. 2, the lamp unit 2102 having a high pressure electricdischarge lamp such as an ultra high pressure mercury lamp as a whitelight source is installed in the inside of the projector 10. Theprojection light projected from the lamp unit 2102 is separated to threeprimary colors of R(red), G(green) and B(blue) by three mirrors 2106 andtwo dichroic mirrors 2108 which are disposed therein. The separatedprojection light is respectively led to a light valves 100R, 100G and100B corresponding to each primary color. Further, since the light of Bcolor is longer in the light path than light of other R color or Gcolor, the light of B color is led through a relay lens 2121 having anincident lens 2122, a relay lens 2123 and an emission lens 2124 in orderto prevent loss thereof.

In the projector 10, each of the light valves 100R, 100G and 100B ismade from a liquid crystal panel in which the transmissivity may be setper pixel. Picture signals appointing gradation levels of the primarycolor components of each of the R color, G color and B color aresupplied to light valves 100R, 100G and 100B and in accordance with thesupplied picture signals, the light valves 100R, 100G and 100B aredriven respectively. The light modulated by the light valves 100R, 100Gand 100B is incident from three directions in a dichroic prism 2112. Inthe dichroic prism 2112, the light of R color and B color is reflectedat 90 degree, light of G color goes straightly. Accordingly, image ofeach primary color are combined and thereafter, the combined colorimages are projected on the screen SC by a projection lens group 2114.

Further, in light valves 100R, 100G and 100B, since light correspondingto R color, G color and B color respectively is incident by thediachronic mirror 2108, there is no need to install a color filter.Further, while transmitted images of light valves 100R and 100B arereflected by the dichroic prism 2112 and then are projected, while thetransmitted image of light valve 100G is projected as is. Accordingly,it is constituted such that a horizontal scanning direction by the lightvalves 100R and 100B is reversed with respect to the horizontal scanningdirection by the light valve 100G and thereby an image which is reversedright to left is displayed. In addition, in FIG. 2, the liquid crystalpanel consisted of light valves 100R, 100G and 100B is a transmissiontype and is constituted by a transmission type projector, but areflective type may be used as the liquid crystal panel to constitute areflective type projector.

FIG. 3 shows a diagram illustrating the external appearance of theglasses 20. As shown in FIG. 3, the glasses 20 have a frame 201 and aright eye shutter 206R and a left eye shutter 206L are installed in theportion corresponding to lenses of the general glasses for visioncorrection. The right eye shutter 206R and the left eye shutter 206L arean example of a liquid crystal shutter and are opened and closedaccording to a shutter synchronization signal transmitted from theprojector 10, which will be described later. Herein, if the right eyeshutter 206R and the left eye shutter 206L are “open”, it refers thattransmissivity is in a level higher than a predetermined threshold value(for example, 5%), and if “closed”, it refers that transmissivity is ina level lower than a predetermined threshold value (for example, 5%).Further, the glasses 20 have an infrared ray receiving section 204installed on a front surface (that is, the surface toward the front ofuser when the glasses 20 are worn by a user) of the frame 201. Theinfrared ray receiving section 204 has for example, light receivingelements such as photodiodes and receives a shutter synchronizationsignal transmitted by infrared transmission from the projector 10.

FIG. 4 is a block diagram illustrating a functional configuration ofdisplay system 1 including the projector 10, the glasses 20 and thescreen SC. As shown in FIG. 4, the projector 10 has a picture signalacquisition section 11, a picture signal processing section 12, a lampdrive section 13, a picture projection section 14, a synchronizationsignal creation section 15 and an infrared ray emission section 16.Functions of the picture signal acquisition section 11, the picturesignal processing section 12, the lamp drive section 13 and thesynchronization signal creation section 15 may be realized by executinga program stored in a storage device such as ROM (Read Only Memory) orhard disk by the operation processors such as CPU (Central ProcessingUnit).

The picture signal acquisition section 11 acquires picture signal fromthe external device such as DVD (Digital Versatile Disc) player orpersonal computer. When the picture signal is stored in the storagedevice such as a hard disk provided in the projector 10, the picturesignal acquisition section 11 may acquire picture signal from thestorage device. As described above, in this example, it is assumed thatthe picture signal which the picture signal acquisition section 11acquires is a picture signal (hereinafter, referring to as 3D picturesignal) displaying a 3D picture. The 3D picture signal acquired by thepicture signal acquisition section 11 is inputted to the picture signalprocessing section 12.

The picture signal processing section 12 performs various processes withrespect to the picture signal inputted from the picture signalacquisition section 11. The process that the picture signal processingsection 12 includes process of separating the picture signal of eachcolor of RGB in picture signal inputted from the picture signalacquisition section 11 and supplying the separated picture signal tolight valves 100R, 100G and 100B of the picture projection section 14.Further, the picture signal processing section 12 creates a writingstart signal (referred to as start pulse) indicating a timing (that is,a scanning start timing of light valves 100R, 100G and 100B) whenwriting data of each image consisting of picture indicated by thepicture signal to light valves 100R, 100G and 100B and then supplies tothe lamp drive section 13 and the synchronization signal creationsection 15. Further, a period from writing start of an image data towriting start of a next image data refers to a frame interval. Thewriting start signal is an example of a signal indicating a displayperiod of the right eye image and the left eye image of a 3D picture.

The lamp drive section 13 creates a lamp drive current that drives thelamp unit 2102 of the picture projection section 14, based on thewriting start signal supplied from the picture signal processing section12. An explanation of the creation of lamp drive current will bedescribed later.

A configuration of the picture projection section 14 is illustrated byan example in FIG. 2. The picture signal of RGB inputted to the pictureprojection section 14 from the picture signal processing section 12 usesfor control of light valves 100R, 100G and 100B of the pictureprojection section 14 and the picture projection section 14 projectspicture according to the picture signal to the screen SC. Since thepicture signal supplied to the picture projection section 14 from thepicture signal processing section 12 is a 3D picture signal, the pictureprojection section 14 performs a time division of the right eye imageand the left eye image including image indicating by 3D picture signaland projects them to the screen SC to alternately display on the screenSC.

The synchronization signal creation section 15 creates a shuttersynchronization signal, based on the writing start signal supplied fromthe picture signal processing section 12. Herein, the shuttersynchronization signal is a signal indicating a control timing whencontrolling the right eye shutter 206R and the left eye shutter 206L ofthe glasses 20 so that the right eye shutter 206R of the glasses 20 isin an opened state and the left eye shutter 206L is in a closed statewhen the right eye image is displayed in the screen SC and the right eyeshutter 206R of the glasses 20 is in the closed state and the left eyeshutter 206L is in the opened state when the left eye image is displayedon the screen SC (that is, to open and close the shutters 206R and 206Lin synchronization with image displayed on the screen SC). The shuttersynchronization signal may be a signal indicating both sides of a timingwhich the shutters 206R and 206L stands in the opened state and a timingwhich the shutters stands in the closed state. Alternatively, when theshutters 206R and 206L are set so that the closed (or opened) statebecomes after lapse of a predetermined time after the opened (or closed)state becomes, the shutter synchronization signal may be a signalindicating only the timing that the shutters 206R and 206L stands in theopened (or closed) state.

The infrared ray emission section 16 has an infrared ray emissionelement such as LED (Light Emitting Diode) for example, and transmitsthe shutter synchronization signal created by the synchronization signalcreation section 15 through the infrared transmission to the glasses 20.The infrared ray emission section 16 is installed as a separate bodyfrom the main body of the projector 10 and may be connected through wireor wireless to the main body of the projector 10. In such a case, theinfrared ray emission section 16 is disposed to face toward userconfronting the screen SC near the screen SC and the shuttersynchronization signal sent from the infrared ray emission section 16may be received by the infrared ray receiving section 204 of the glasses20 which wears by a user. Alternatively, it is preferable such that theinfrared ray emission section 16 is integrally installed with the mainbody of the projector 10 and the shutter synchronization signal istransmitted from the infrared ray emission section 16 toward the screenSC and the shutter synchronization signal reflected by the screen SC isreceived by the infrared ray receiving section 204 of the glasses 20.The synchronization signal creation section 15 and the infrared rayemission section 16 are an example of the synchronization signaltransmission section of the invention.

The glasses 20 have a shutter drive section 210 in addition to theinfrared ray receiving section 204 and the shutters 206R and 206L whichare shown in FIG. 3. The function of the shutter drive section 210 maybe realized by executing a program stored in the storage device such asROM or flash memory by an operation process device such as CPU.

The shutter drive section 210 performs the opening and closing operationof the shutters 206R and 206L of the glasses 20, based on the shuttersynchronization signal received by the infrared ray receiving section204. The shutter drive section 210 stops the opening and closingoperation of the shutters 206R and 206L when the shutter synchronizationsignal is not received by the infrared ray receiving section 204(shutters 206R and 206L are in the opened state).

FIG. 5 shows a block diagram illustrating a configuration of the lampdrive section 13. The lamp drive section 13 has a AC-DC converter 131, aDC-AC converter 132 and a controller 133. The controller 133 may be anoperation processing device executing a program stored in a storagedevice such as a ROM. The AC-DC converter 131 has input terminals K1 andK2 to which an AC power supply voltage, which is not shown in thedrawing, is applied and creates a direct current of the size dependingon a control signal from the controller 133. The AC-DC converter 131 mayinclude a rectifying bridge in which the AC power supply voltage appliedto input terminals K1 and K2 is converted to direct current in similarmanner to the unit I which is shown in FIG. 2 of JP-T-10-501919, forexample, and a down converter (DC-DC converter) in which the magnitudeof the direct current outputted from the rectifying bridge is convertedaccording to a control signal from the controller 133.

The DC-AC converter 132 converts the direct current supplied from theAC-DC converter 131 to AC lamp drive current and supplies the convertedcurrent to the lamp unit 2102. The DC-AC converter 132 may be a bridgecircuit which consists of switching elements such as transistors orthyristors, for example. The on/off timing of the switching element iscontrolled by the control signal from the controller 133 and thereby, aperiod or phase (that is, polarity switching timing) of the AC lampdrive current outputted from the DC-AC converter 132 is controlled. TheDC-AC converter 132 may be a circuit configuration similar to a unit IIshown in FIG. 2 of the JP-T-10-501919, for example.

The controller 133 creates a control signal for operating on/offswitching element of the bridge circuit which is included in the DC-ACconverter 132 such that the AC lamp drive current which is synchronizedwith the writing start signal (start pulse) inputted from the picturesignal processing section 12 is supplied to the lamp unit 2102. Further,the controller 133 creates a control signal for controlling an outputcurrent of the AC-DC converter 131 such that the lamp drive current hasa peak (current pulse) where only a predetermined delay time is out ofphase with respect to the writing start signal.

FIG. 6 shows a graph illustrating an example of the lamp drive currentand the lamp brightness. As shown in FIG. 6, the writing start signal isa pulse train having a predetermined period corresponding to one frameperiod. The lamp drive current supplied to the lamp unit 2102 from theDC-AC converter 132 is a current in which a pulse formed-current(hereinafter, refer to as a current pulse) PI of the same polarity asthe half wave at the time of half wave termination of each polarity ofAC current with square wave form in which an amplitude is I m and inwhich has a period corresponding to the writing start signal isoverlapped and has a peak amplitude Ip in a portion that the currentpulse PI is overlapped. Like that, by overlapping the current pulse PIto AC current, temperature of electrode rises and a stability of theelectric discharge ark increases (for example, refer to JP-T-10-501919).In this example, the current pulse PI has a phase delayed by only thefirst delay time Td1 with respect to the writing start signal and apulse width ΔT.

The lamp drive current shown in FIG. 6, under the control of controller133, operates on/off a switching element of the bridge circuit includedin DC-AC converter 132, in the timing delayed by the second delay timeTd2=Td1+ΔT from the writing signal to create AC current of square waveform by which a polarity is switched in a timing delayed by a seconddelay time Td2=Td1+ΔT from writing signal and also to create volume ofoutput current of AC-DC convertor 131 by increasing by a period ΔTpredetermined corresponding to the pulse width in a timing delayed bythe first delay time Td1 display system from writing signal. That is,the first delay time Td1 indicates a creation timing of the currentpulse (peak) in lamp drive current and the second delay time Td2indicates a timing in which polarity of the lamp drive current isswitched over. The controller 133 adjusts the first delay time Td1 byadjusting the creation timing of the control signal to the AC-DCconverter 131 and adjusts the second delay time Td2 by adjusting thecreation timing of the control signal to the DC-AC converter 132.

In a case where the lamp drive signal as mentioned above is supplied,the strength (referred to as a lamp brightness) of the light createdfrom the lamp unit 2102 is represented with a graph in the lowest stageof FIG. 6. The lamp brightness changes according to the volume (absolutevalue) of current supplied to the lamp unit 2102. As shown in thedrawing, the lamp brightness has a pulse PL (referred to as a lampbrightness pulse) of the peak value Lp corresponding to the currentpulse PI of lamp drive current. Further, the lamp brightness hassubstantially constant value Lm corresponding to the AC current withsquare wave form in a case where the current pulse PI is not overlappedin a portion between adjacent lamp brightness pulses PL.

FIG. 7 shows a diagram illustrating creation timing of lamp brightnesspulse PL with respect to operation of each section of the display system1 in the embodiment. Further, in description in below, in a case wherethere is no need to distinguish the liquid crystal panels (light valves)100R, 100G and 100B from each other, they are collectively referred toas a liquid crystal panel 100. As shown in FIG. 7, the right eye imageand the left eye image are alternately displayed on the liquid crystalpanel 100 in the predetermined period (frame period). The writing toliquid crystal panel 100 of data (referred to as a image data)representing each image displayed on the liquid crystal panel 100 isstarted corresponding to the creation of the writing start signal (startpulse). Herein, because it takes a predetermined time to writing theimage data for one image to the liquid crystal panel 100, the periodfrom a certain writing start signal creation until the writing of theimage data corresponding to the writing start signal is finished is thata part of the new image (for example, a right eye image) correspondingto the pixel that the writing is finished and a part of the previousimage (for example, a left eye image) corresponding to the pixel thatthe writing is not finished are mixed and displayed.

The right eye shutter 206R of glasses 20 is controlled to be opened whenthe right eye image is displayed on liquid crystal panel 100 and theleft eye shutter 206L is controlled to be opened when the left eye imageis displayed on liquid crystal panel 100, based on the shuttersynchronization signal transmitted from projector 10. More specifically,the right eye shutter 206R is controlled to be opened in the later halfportion of the frame period in which the right eye image is displayedand to be closed during the remaining period. The left eye shutter 206Lis controlled to be opened in later half portion of the frame period inwhich the left eye is image displayed and to be closed in the remainingperiod. The control of the right eye shutter 206R and the left eyeshutter 206L like that, for example, in the synchronization signalcreation section 15 of the projector 10 is realized by creating theshutter synchronization signal delayed by the predetermined delay time(in this example, a half of the frame period) from the writing startsignal and by transmitting the created signal through the infrared rayemission section 16 to the glasses 20.

As described above, during a predetermined period from the start of eachimage frame period, a part of the right eye image and a part of the lefteye image are mixed and displayed. Because of that, if during thatperiod, the right eye shutter 206R or the left eye shutter 206L is in anopened state, the right eye image and the left eye image arrive at theright eye or the left eye (that is, crosstalk occurs) of the userwithout separating the right eye image and the left eye image. By makingsuch a way that the right eye shutter 206R and the left eye shutter 206Lbe in an opened state only in a later half portion of the frame periodof the corresponding image, the right eye shutter 206R or the left eyeshutter 206L being in an opened state during a period in which a part ofright eye image and a part of the left eye image are mixed and displayedand the right eye image and the left eye image arrives to the right eyeor the left eye of the user without separating of the right eye imageand the left eye image is prevented. Further, which part of the frameperiod of corresponding image allows the right eye shutter 206R and theleft eye shutter 206L to be in the opened state may be adjusteddepending on the time required to the writing of image data and is notlimited to the later half portion. For example, in a case where thewriting of image data terminates in a quarter time of the frame period,the right eye shutter 206R and the left eye shutter 206L may be in theopened state during the remaining period (that is, three quarter periodbefore the termination of the frame period). In other words, the righteye shutter 206R and the left eye shutter 206L may stand in the openedstate in a part of frame period so that the right eye shutter 206R orleft eye shutter 206L does not become the opened state during the periodwhen a part of the left eye image and a part of the right eye image aremixed and is displayed.

As shown in FIG. 7, in the embodiment, the lamp brightness pulse PL isoverlapped with the period when the right eye shutter 206R is opened andthe period when the left eye shutter 206L is opened. As described withreference to FIG. 6, the lamp brightness pulse PL corresponds to thecurrent pulse PI in the lamp drive current supplied to the lamp unit2102. That is, the first delay time Td1 which is a delay time of currentpulse PI with respect to the writing start signal is adjusted so thatthe current pulse PI (that is, the peak of the lamp drive current) isoverlapped with the period when the right eye shutter 206R is opened andthe period when the left eye shutter 206L is opened and thereby, thecontroller 133 of the lamp drive section 13 shown in FIG. 5 creates AClamp drive current in which the current pulse PI is overlapped, based onthe first delay time Td1 that is set like that. In other words, the lampdrive section 13 supplies the lamp driving current having the currentpulse PI overlapping with period in which the right eye shutter 206R isopened and the current pulse PI overlapping with period in which theleft eye shutter 206L is opened to the lamp unit 2102. Further, thesecond delay time Td2 indicating a polarity switching timing of lampdrive current is set, based on the first delay time Td1 and the width ΔTof the current pulse PI so that the current pulse PI of lamp drivecurrent is created at the termination portion of the half wave of eachpolarity of lamp drive current.

In FIG. 7, right eye optical intensity and left eye optical intensityindicate the optical intensity passed through the right eye shutter 206Rand the left eye shutter 206L of the glasses 20 disposed toward thescreen SC when displaying a predetermined common image (for example,image of the full-screen white) as the right eye image and the left eyeimage on the screen SC under control of the liquid crystal panel 100.The right eye optical intensity is substantially proportional to theproduct of transmissivity of the right eye shutter 206R and the lampbrightness, and the left eye optical intensity is substantiallyproportional to the product of transmissivity of the left eye shutter206L and the lamp brightness. Herein, for simplicity, it is assumed thatthe transmissivity in the opened state of the right eye shutter 206R andthe left eye shutter 206L is constant. As shown in drawing, the righteye optical intensity is substantially zero during the closing period ofthe right eye shutter 206R, and has a substantially constant value in aportion that is not overlapped with the lamp brightness pulse PL, andthe pulse-shape value increases in a portion which is overlapped withthe lamp brightness pulse PL during the opening period of the right eyeshutter 206R. Similarly, the left eye optical intensity is substantiallyzero during the closing period of the left eye shutter 206L, and hassubstantially constant value in a portion that is not overlapped withlamp brightness pulse PL during the opening period of the left eyeshutter 206L, and the pulse-shape value is increased in a portion whichis overlapped with lamp brightness pulse PL.

FIG. 8 shows a diagram illustrating a creation timing of the lampbrightness pulse PL with respect to the operation of each section of thedisplay system 1 in a comparative example. In the example shown in FIG.8, a point that neither a period in which the right eye shutter 206R isopened nor a period in which the left eye shutter 206L is opened isoverlapped is different from the example shown in FIG. 7. Because ofthat, in the example shown in FIG. 8, the right eye optical intensityand the left eye optical intensity are substantially constant value thatthere is no a portion that the pulse-shape value is increased during theperiod which the right eye shutter 206R is opened and the left eyesshutter 206L is opened.

The brightness of the image which user who wears the glasses 20 andenjoys the image that is projected on screen senses depends on a value(that is, time average) which is obtained by a integrating for opticalintensity (that is, right eye optical intensity and left eye opticalintensity) passing through the right eye shutter 206R and the left eyeshutter 206L during each frame period (an example of a predeterminedperiod). Accordingly, in the example shown in FIG. 8, compared to theexample shown in FIG. 7, the time-integrating value for opticalintensity is small as much as there is not a part increasing into pulseform corresponding to lamp brightness pulse PL in the right eye opticalintensity and the left eye optical intensity, and the brightness of theimage which the user who wears the glasses 20 senses decreases. In otherwords, in the embodiment shown in FIG. 7, because the phase (that is,first delay time Td1 for the writing start signal) of the peak of thelamp driving current is set so that a peak (current pulse PI) of thelamp driving current is overlapped with the period when the right eyeshutter 206R is opened and the period when left eye shutter 206L isopened, the brightness of an image viewed through the glasses 20 by auser is improved in comparison to the case that a peak of the lampdriving current is not overlapped with neither a period when the righteye shutter 206R is opened nor a period when the left eye shutter 206Lis opened.

In the example shown in FIG. 7 and FIG. 8, for simplicity, it is assumedthat the transmissivity in the opened state of the right eye shutter206R and the left eye shutter 206L is constant. However, in actualpractice, the transmissivity in the opened state of the right eyeshutter 206R and the left eye shutter 206L is not constant but changes.

FIG. 9 shows a diagram illustrating a transmissivity of the glasses 20and lamp brightness in the comparative example. In FIG. 9, the solidline indicates lamp brightness and the peak value is relativelyindicated as 1. Further, the dotted line indicates the transmissivity ofthe right eye shutter 206R and indicates relatively its maximum valueas 1. Similarly, one dot and dashed line relatively indicatestransmissivity of the left eye shutter 206L and indicates its maximumvalue as 1. In FIG. 9, when the transmissivity of the right eye shutter206R and the left eye shutter 206L is greater than a predetermined value(for example, relative value is 0.1), it is said that the right eyeshutter 206R or the left eye shutter 206L is in an opened state. Asshown in drawing, in the opened state, after each transmissivity of theright eye shutter 206R and the left eye shutter 206L gently rises up fora while, after initially rising rapidly. And then, after instructing astate change into a closing state, the transmissivity rapidly drops.That is to say, a square wave represents a corrupted shape. Similarly,the transmissivity of the right eye shutter 206R and the left eyeshutter 206L changes in non-uniformly in the opened state. In theexample shown in FIG. 9, the lamp brightness pulse PL does not overlapwith either a period in which the right eye shutter 206R is opened or aperiod in which the left eye shutter 206L is opened.

FIG. 10 shows a diagram illustrating an optical intensity measured overthe glasses 20 in the example shown in FIG. 9. Herein, the opticalintensity measured over the glasses 20 is the optical intensity passingthrough the right eye shutter 206R and the left eye shutter 206L of theglasses 20 which are disposed toward the screen SC when the liquidcrystal panel 100 is controlled and a common image (for example, animage of the full-screen white color) determined in advance as a righteye image and a left eye image in the screen SC is displayed, in thesame manner that has been described with reference to FIG. 7 and FIG. 8.In FIG. 10, the dotted line indicates an optical intensity passedthrough the right eye shutter 206R and one dot and dashed line indicatesan optical intensity passed through the left eye shutter 206L. Theoptical intensity relatively indicates the optical intensity measuredwhen a relative value of the transmissivity of the shutter is 1 whilethe relative value of lamp brightness is 1, as 1. The optical intensitypassed through the right eye shutter 206R is substantially proportionalto the product of transmissivity of the right eye shutter 206R and thelamp brightness and the optical intensity passed through the left eyeshutter 206L is substantially proportional to the product oftransmissivity of the left eye shutter 206L and the lamp brightness. Asdescribed above, in the example shown in FIG. 9, the lamp brightnesspulse PL does not overlap with either a period in which the right eyeshutter 206R is opened or a period in which the left eye shutter 206L isopened, because of that, the optical intensity measured over the glasses20 shown in FIG. 10 becomes a wave form that there is no portionincreasing in pulse form corresponding to the lamp brightness pulse PL.

FIG. 11 shows a diagram illustrating a transmissivity of the glasses 20and the lamp brightness in an embodiment. FIG. 12 shows a diagramillustrating an optical intensity measured over the glasses 20 in theexample shown in FIG. 11. In example of FIG. 11, the lamp brightnesspulse PL is different from FIG. 9 in that the opening period of theright eye shutter 206R and the opening period of the left eye shutter206L overlap. More specifically, in the example of FIG. 11, a point thatthe trasmissivity of the right eye shutter 206R or the transmissivity ofthe left eye shutter 206L becomes the maximum substantially accords withfalling of the lamp brightness pulse PL. As a result, as shown in FIG.12, the optical intensity measured over the glasses 20 stands for a waveform having a portion increasing in pulse form corresponding to the lampbrightness pulse PL. Thereby, if it is assumed that the value obtainedby integrating the optical intensity measured over the glasses 20 shownFIG. 10 over one frame period is 100, the value obtained by integratingthe optical intensity measured over the glasses 20 shown in FIG. 12 overone frame period is 105.6 and increases by 5.6%. That is, the brightnessof image viewed through the glasses 20 by a user increases by 5.6%.

2. Another Embodiment

The invention is not limited to the embodiment described above, variousmodifications of the embodiment can be realized. The ModificationExample will be described hereinafter. Among the modificationembodiments in below, two or more modification examples may be combined.

2-1. Modification Example 1

In the example illustrating in FIG. 11 and FIG. 12 of the above theembodiment, the point that the transmissivity of the right eye shutter206R or the transmissivity of the left eye shutter 206L becomes themaximum value substantially accords with falling of the lamp brightnesspulse PL, but the invention is not limited thereto. If the openingperiod of the right eye shutter 206R and the opening period of the lefteye shutter 206L overlap each other, the creation timing of lampbrightness pulse PL (that is, creation timing of current pulse PI) maybe changed variously.

FIG. 13 shows a diagram illustrating transmissivity of the glasses 20and lamp brightness related to the Modification Example 1. Further, FIG.14 shows optical intensity measured over the glasses 20 in the exampleshown in FIG. 13. In example of FIG. 13, before when the transmissivityof the right eye shutter 206R or the left eye shutter 206L becomes amaximum value, at the time when the relative value of transmissivity isapproximately 0.8, a point that a period in which the right eye shutter206R is opened and a period in which the left eye shutter 206L is openedare overlapped is different from an example of FIG. 11. In such a case,as shown in FIG. 14, the optical intensity measured over the glasses 20has a portion increasing in pulse form corresponding to the lampbrightness pulse PL. Thereby, if it is assumed that a value whichoptical intensity measured over the glasses 20 shown in FIG. 10 isobtained by integrating over one frame period is 100, a value thatoptical intensity measured over the glasses 20 shown in FIG. 14 isobtained by integrating over one frame period becomes 104.4 andincreases by 4.4%. That is, brightness of image viewed through theglasses 20 by a user increases by 4.4%.

In example shown in FIG. 13 and FIG. 14, in comparison with a case wherelamp brightness pulse PL is not overlap with none of the opening periodof the right eye shutter 206R and opening period of the left eye shutter206L, brightness of image viewed through the glasses 20 by a userincreases. However, in the examples shown in FIG. 13 and FIG. 14, incomparison with examples shown in FIG. 11 and FIG. 12, thetime-integrating value of one frame period of optical intensity measuredover the glasses 20 is small. Like that, even though lamp brightnesspulse PL is overlapped with a period in which the right eye shutter 206Ris opened and a period in which the left eye shutter 206L is opened, bya phase relationship between the lamp brightness pulses PL, and a periodin which the right eye shutter 206R is opened and a period in which theleft eye shutter 206L is opened, the time-integrating value of one frameperiod of optical intensity measured over the glasses 20 changes.Accordingly, the phase (that is, phase of current pulse PI) of the lampbrightness pulse PL may be adjusted by the controller 133 of the lampdrive section 13 so that the time-integrating value of one frame periodof the optical intensity measured over the glasses 20 grows big as muchas possible. Further, the optical intensity measured over the glasses 20is approximately proportional to the product of lamp brightness andtransmissivity of shutters 20R and 20L of the glasses 20 as describedabove. Accordingly, the lamp drive current having a peak (current pulsePI) may be controlled by controller 133 so that the integral value ofone frame period of the product of lamp brightness and transmissivity ofshutters 20R and 20L of the glasses 20 becomes the maximum value.

2-2. Modification Example 2

FIG. 15 shows a diagram illustrating a transmissivity of the glasses 20and lamp brightness related to the Modification Example 2. Further, FIG.16 shows an optical intensity measured over the glasses 20 in theexample shown in FIG. 15. In the example of FIG. 15, the width (that is,width ΔT of the current pulse PI) of the lamp brightness pulse PL iswider (approximately, three times) than the width of the lamp brightnesspulse PL shown in FIG. 11. In addition, it is different from the exampleshown in FIG. 11 in a point that a value (relative value for brightnessLp of lamp brightness pulse PL) of a substantially constant lampbrightness Lm in the part between the lamp brightness pulses PL next toeach other is smaller than a value of lamp brightness Lm in the exampleshown in FIG. 11. In the example of FIG. 15, a point that thetransmissivity of the right eye shutter 206R or the transmissivity ofthe left eye shutter 206L becomes the maximum value substantiallyaccords with falling of the lamp brightness pulse PL in similar mannerto the example shown in FIG. 11 substantially accords. As a result, asshown in FIG. 16, the optical intensity measured over the glasses 20becomes a wave form having a portion increasing in a pulse formcorresponding to the lamp brightness pulse PL. Thereby, if it is assumedthat the value which the optical intensity measured over the glasses 20shown in FIG. 10 is obtained by the integrating over one frame period is100, a value that the optical intensity measured over the glasses 20shown in FIG. 16 is obtained by a integrating over one frame periodbecomes 120.8 and increases 20.8%. The value is greater than the value105.6 which the optical intensity measured over the glasses 20 shown inFIG. 12 corresponding to the example of FIG. 11 is obtained byintegrating over one frame period.

Similarly, compared to the examples shown in FIG. 15 and FIG. 16 withthe examples shown in FIG. 11 and FIG. 12, in spite of that a value oflamp brightness Lm in the part between the lamp brightness pulses PLnext to each other decreases, the time-integrating value in one frameperiod of the optical intensity measured over the glasses 20 is improvedby increasing the width of the lamp brightness pulse PL. Accordingly,improving of the brightness of image viewed through the glasses 20 by auser and suppressing of lamp consumed power are compatible. Further, bydecreasing the lamp brightness Lm in the part between the lampbrightness pulses PL next to each other, the lamp brightness (that is,brightness of image which is displayed at that time) in a period inwhich all of the right eye shutter 206R and the left eye shutter 206Lare in a closed state decreases compared to that in a period in whicheither of the right eye shutter 206R and the left eye shutter 206L is inan opened state. Thereby, a crosstalk created due to a limitation to anopening and closing speed (that is, response speed of liquid crystal) ofthe right eye shutter 206R and the left eye shutter 206L and the like isdecreased compared to a case where the lamp brightness Lm in the periodis not decreased.

2-3. Modification Example 3

In the above the embodiment, an ultra high pressure mercury lamp as ahigh pressure electric discharge lamp driven by an AC current has beenused, the invention is not limited thereto. For example, the highpressure electric discharge lamp may be as a metal halide lamp. Ifdriving current has the peak synchronized in a picture signal, and thebrightness depended on volume of the driving current is a lamp emittinglight, any lamp may be used.

2-4. Modification Example 4

In the above the embodiment, a shutter synchronization signal has beentransmitted to the glasses 20 by infrared ray transmission by theinfrared ray emission section 16, but the invention is not limitedthereto. The shutter synchronization signal may be transmitted using aunit other than infrared ray transmission. For example, the shuttersynchronization signal may be transmitted by the wireless.

2-5. Modification Example 5

In the above embodiment, the output current of the AC-DC convertor ofthe lamp drive section 13 has been controlled so that the current pulsePI of the lamp drive current creates in a termination portion of halfwave of each polarity of the AC lamp drive current, the invention is notlimited thereto. Output current of the AC-DC convertor of the lamp drivesection 13 may be controlled so that the current pulse PI creates in astarting portion or a middle portion of half wave of each polarity ofthe AC lamp drive current. Further, the lamp drive current is notlimited to that pulse is overlapped with AC current of square wave shapeand may be AC current of triangular or sinusoidal wave shape.

2-6. Modification Example 6

In the above the embodiment, the projector 10 is a three panel typeprojector in which uses three light valves 100R, 100G and 100B, but theinvention is not limited thereto. The projector 10 may be a single paneltype projector in which uses one color liquid crystal panel havingpixels of each color of RGB.

What is claimed is:
 1. A projector comprising: a light valve which isdriven in accordance with a first image signal in a first period and asecond image signal in a second period in a time division manner; alight source unit which emit a light toward the light valve; and a lightsource drive section that supplies a light source drive current to thelight source unit; wherein the light source drive section supply a firstdrive current so as to the light source unit emits a first brightness ina first part of the first period, the first part of the first period isincluded within the first period, and the first brightness is a maximumbrightness in the first period, and the light source drive sectionsupply a second drive current so as to the light source unit emits asecond brightness in a second part of the second period, the second partof the second period is included within the second period, and thesecond brightness is a maximum brightness in the second period.
 2. Theprojector according to claim 1, a length of the first part of the firstperiod is same as a length of the second part of the second period. 3.The projector according to claim 1, a length of the first period is sameas a length of the second period.
 4. The projector according to claim 1,the first part of the first period is apart from the second period andthe second part of the second period is apart from the first period. 5.The projector according to claim 1, the projector projects 3D image andthe first image signal is a right eye image signal and the second imagesignal is a left eye image signal.
 6. The projector according to claim1, further comprising a picture signal processing section which controlthe first image signal and the second image signal, and controls thelight drive section.